1. Field
This disclosure relates to a polymer for optical film, and to an optical film including the polymer.
2. Description of the Related Art
Flat panel displays may be classified into emitting display devices that emit light by themselves and non-emitting display devices that require separate light sources. Optical compensation films such as phase difference films may be often used for improving image quality of the flat panel displays.
In an emitting display device, for example, an organic light emitting display, visibility and contrast ratio may be decreased due to reflection of external light by metal such as an electrode in the display device. In order to reduce such deterioration, a polarizing plate and a phase difference film are used to prevent the external light reflected in the display device from leaking out of the display device.
In a liquid crystal display (“LCD”), which is a kind of non-emitting display device, elliptical polarization and light leakage may occur due to birefringence of liquid crystal and crossed polarizing plates in the display device, thereby decreasing contrast ratio and causing color shift. As for the liquid crystal display, the device may become thicker due to the thickness of the liquid crystal, and thus the thickness retardation (“Rth”) may be a more serious than the in-plane retardation (“Re”).
Meanwhile, a need for a flexible display, which is thin and light as a paper, which requires low electric power, and which can be carried without being limited to the place or time, increases. In order to realize the flexible display, a substrate for the flexible display, organic or inorganic material to be processed, flexible electronics, encapsulating and packaging technology, and etc., are strongly desired. Among them, the flexible substrate may be the most important material defining performance, reliability, and price of the flexible display.
Plastic substrates may be useful for manufacturing flexible displays due to the processability, low weight, and compatibility to continuous process. However, since plastic substrates are unstable to heat, their properties need to be improved for use in the flexible displays.
Accordingly, a colorless and transparent material having high temperature stability, low coefficient of thermal expansion (“CTE”), high mechanical strength, and low optical anisotropy is desired to prepare an optical film.